<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <style>
      * {
        margin: 0;
        padding: 0;
      }
      body {
        height: 3000px;
      }
      .header {
        height: 100px;
        font-size: 33px;
        background-color: #b6db3c;
        line-height: 100px;
        text-align: center;
      }
      .item {
        background-color: #f2f4b2;
      }
      .item-a {
        font-size: 40px;
        background-color: #b03f0a;
        /* 粘性布局 */
        position: sticky;
        top: 0;
      }
      .item-b {
        font-size: 40px;
        background-color: #86b00a;
        position: sticky;
        top: 0;
      }
      .item-c {
        font-size: 40px;
        background-color: #0a7eb0;
        position: sticky;
        top: 0;
      }
    </style>
  </head>
  <body>
    <!-- 头部 -->
    <div class="header">header</div>
    <!-- 内容区域 -->
    <div class="content">
      <div class="item">
        <div class="item-a">A</div>
        <h2>AAAA</h2>
        <h2>AAAA</h2>
        <h2>AAAA</h2>
        <h2>AAAA</h2>
        <h2>AAAA</h2>
        <h2>AAAA</h2>
        <h2>AAAA</h2>
        <h2>AAAA</h2>
        <h2>AAAA</h2>
        <h2>AAAA</h2>
        <h2>AAAA</h2>
      </div>
      <div class="item">
        <div class="item-b">B</div>
        <h2>BBBB</h2>
        <h2>BBBB</h2>
        <h2>BBBB</h2>
        <h2>BBBB</h2>
        <h2>BBBB</h2>
        <h2>BBBB</h2>
        <h2>BBBB</h2>
        <h2>BBBB</h2>
        <h2>BBBB</h2>
        <h2>BBBB</h2>
        <h2>BBBB</h2>
      </div>
      <div class="item">
        <div class="item-c">C</div>
        <h2>CCCC</h2>
        <h2>CCCC</h2>
        <h2>CCCC</h2>
        <h2>CCCC</h2>
        <h2>CCCC</h2>
        <h2>CCCC</h2>
        <h2>CCCC</h2>
        <h2>CCCC</h2>
        <h2>CCCC</h2>
        <h2>CCCC</h2>
        <h2>CCCC</h2>
      </div>
    </div>
  </body>
</html>
